The Darkening Sea

ANNALS OF SCIENCE about climate change and the ocean… Writer describes the work of Victoria Fabry, an oceanographer who studies tiny marine organisms called pterapods. As part of her research, she noted that increased carbon dioxide (CO2) in the water caused the pterapod shells to dissolve… Writer describes the large quantities of carbon dioxide that have been added to the atmosphere since the start of the industrial revolution by the burning of fossil fuels. Gasses from the atmosphere are absorbed by the ocean. Nearly half of all the carbon dioxide that humans have emitted since the start of the nineteenth century has been absorbed by the sea. In sufficient quantities, CO2 can change the pH of ocean water. This process is known as “ocean acidification.” It is impossible to reverse the acidification that has already taken place and the oceans will continue to soak up carbon until they reach a new equilibrium with the air. The question that remains is how marine life will respond… Discusses the work of climate scientists Ken Caldeira and Michael Wickett, who coined the term “ocean acidification.” Caldeira is a climate modeller. In 1999 he did some work for the Department of Energy who wanted to know what the environmental consequences would be of capturing CO2 from smokestacks and injecting it deep into the sea. Caldeira discusses how altering the pH of ocean water would affect the way ocean organisms form their shells. Caldeira found that, under present circumstances, the oceans would become undersaturated with aragonite-the form of calcium carbonate produced by pterapods and corals-by the year 2300. Organism that build calcium carbonate shells would be at risk of extinction… Discusses the effects of acidification on the world's coral reefs, which are home to an estimated 25% of all fish species. Much of what is known about coral reefs and ocean acidification was originally discovered in Arizona, in the Biosphere 2 project… A lowering of pH levels would cause coral reefs to stop calcifying. Eventually the reefs would begin to shrink. Chris Langdon, a Columbia University professor, estimates that coral reefs will stop growing around the year 2075. He notes that at least three million fish species live in or near coral reefs. It is impossible to know which species will prove to be particularly vulnerable to declining pH… Tells about a recent meeting of paleooceanographers at which this issue was discussed.